1. Field of the Invention
This invention relates generally to thermal shielding for aircraft gas turbine engine vectorable nozzles and, more particularly, to using outer flaps and shields and flap mounted ejectors for shielding and cooling axisymmetric vectorable exhaust nozzles.
2. Discussion of the Background Art
Vectorable nozzles have been developed for military aircraft gas turbine engines to increase the maneuverability of the aircraft both for air to air combat missions and complicated ground attack missions. Vectorable nozzles generally employ flaps to turn or vector the exhaust flow and thrust of the gas turbine engine powering the aircraft. Two dimensional nozzles have been devised which employ relatively flat flaps to direct the pitch or yaw direction of the engine's thrust. Hauer in U.S. Pat. No. 4,994,660, herein incorporated by reference, discloses an Axisymmetric Vectoring Nozzle (AVEN.RTM. nozzle) that provides a means for vectoring the thrust of an axisymmetric convergent/divergent nozzle by universally pivoting the divergent flaps of the nozzle in an asymmetric fashion or in other words pivoting the divergent flaps in radial and tangential directions with respect to the unvectored nozzle centerline.
Vectoring nozzles, and in particular axisymmetric vectoring nozzles of the type disclosed in the Hauer reference, generally employ directionally controllable flaps to vector the aircraft engine's thrust by turning the hot exhaust flow. The hot nozzle flow is contained by a flap and seal arrangement wherein the divergent flaps and seals are pivotally connected to the nozzle throat in a manner permitting 2 degree of freedom (2 DOF) pivotal movement and axial translation of the exhaust nozzle exit. To this end, twistable divergent seals were developed as disclosed in U.S. patent application Ser. 07/475,465 to William C. Lippmeier, entitled "Exhaust Nozzle Flap Seal" assigned to the same assignee, and incorporated herein by reference. A twistable seal was developed to conform to the skewed flap edges of adjacent vectored nozzle divergent flaps.
Hot nozzles emit infrared radiation which is highly undesirable for military combat aircraft. Infrared radiation from gas turbine engines is conventionally suppressed by shielding and cooling the hot metal structures of the engine. The use of outer flaps and seals around the divergent section of variable nozzles is demonstrated in U.S. Pat. No. 4,128,208 by Ryan et al, entitled "Exhaust Nozzle Flap Seal Arrangement" assigned to the same assignee as the present invention. Nozzles also require cooling for structural reasons. Cooling air is conventionally drawn from the fan section or a compressor section of the gas turbine engine which is expensive in terms of fuel and power consumption. Ejecting nozzles such as the type used on some General Electric J79 engine models have employed slot type ejectors to induct ambient cooling air from the atmosphere to supplement the engine supplied cooling air in order to reduce the use of the more expensive engine air. Such engines provided ejector cooling for variable nozzle throats but not for thrust vectoring nozzles such as axisymmetric vectoring exhaust nozzles which have 2 DOF pivoting flaps and seals.
The present invention overcomes these problems by providing a shielding means and a nozzle cooling means for vectoring nozzles and in particular axisymmetric vectoring nozzles to efficiently cool the nozzle and shield it from emitting infrared radiation. These features and advantages will become more readily apparent in the following description when taken in conjunction with the appended drawings.